The present invention relates to the synthesis of aryl substituted silicone fluids by the hydrosilylation of an aryl substituted acetylene, such as phenylacetylene or diphenylacetylene with a hydride-functionalized silicone fluid.
Silicones fluids having a high refractive index, such as about 1.50, are of interest to the hair care products industry. For example, in addition to providing good feel, wet combing, and low static, silicones having a high refractive index can offer a maximum amount of sheen to hair.
It is generally known to those skilled in the silicone art, that a convenient way to increase the refractive index of a polydiorganosiloxane fluid consisting essentially of chemically combined dialkylsiloxy units is to introduce into the polydiorganosiloxane backbone, a significant number of siloxy units having aryl radicals attached to silicon by carbon-silicon bonds.
Various techniques are available for introducing arylsiloxy units into organopolysiloxanes. One method is based on the use of a convenient source of arylsiloxy such as a polydiorganosiloxane having siloxy units with phenyl radicals attached to silicon by carbon-silicon linkages. However, experience has shown that diphenylsiloxane copolymers have a tendency to crystallize at high levels of diphenylsiloxane. The incorporation of aryl radicals, such as a styrl substituent, into a polydiorganosiloxane using a hydrosilylation reaction is also another alternative for increasing arylsilicon substitution.
As reported by L. N. Lewis et al. in Organometallics, 1991, 10,3750, arylacetylenes, such as phenylacetylene, can undergo facile hydrosilylation with monomeric silylhydrides. Diphenylacetylene has been shown by M. Tanaka et al. Bull. Soc. Fr. 1992, 129, 667.b, to undergo dehydrogenative double silylation with a bis(hydrosilane) to give a cyclic unsaturated compounds as the major product.
Additional procedures are constantly being evaluated for providing silicone fluids having high indices of refraction.